Apparatus and method for detecting decrease in tire air pressure and program for detecting decrease in tire air pressure

Abstract

An apparatus includes a rotating wheel speed ratio calculation means for calculating, based on rotation velocity information, a rotating wheel speed ratio between front wheels and rear wheels of the vehicle; a wheel torque calculation means for calculating a wheel torque of the vehicle; an initialization means for obtaining a relation at a normal internal pressure between the wheel torque and the rotating wheel speed ratio between the front wheels and the rear wheels; a storage means for storing the relation obtained; a comparison means for comparing the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained by the wheel torque calculation means and the relation; and a judgment means for judging whether a tire air pressure is decreased or not based on a comparison result.

1. An apparatus for detecting a tire attached to a vehicle having a decreased air pressure, comprising:
 a rotation velocity detection means for periodically detecting rotation velocities of tires of the respective wheels of the vehicle; 
 a rotating wheel speed ratio calculation means for calculating, based on rotation velocity information obtained from the rotation velocity detection means, a rotating wheel speed ratio between front wheels and rear wheels of the vehicle; 
 a wheel torque calculation means for calculating a wheel torque of the vehicle; 
 an initialization means for obtaining a relation at a normal internal pressure between the wheel torque and the rotating wheel speed ratio between the front wheels and the rear wheels; 
 a storage means for storing the relation obtained by the initialization means; 
 a comparison means for comparing the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained by the wheel torque calculation means and the relation stored in the storage means; and 
 a judgment means for judging whether a tire air pressure is decreased or not based on a comparison result by the comparison means. 
 
     
     
       2. The apparatus according to  claim 1 , wherein the initialization means includes a means for obtaining a relation at a normal internal pressure between the wheel torque and the rotating wheel speed ratio between the front wheels and the rear wheels based on a regression line, and
 the comparison means compares the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained by the wheel torque calculation means and the regression line. 
 
     
     
       3. The apparatus according to  claim 1 , wherein the initialization means includes a means for setting a plurality of wheel torque regions and for calculating, at a normal internal pressure, an average value of the rotating wheel speed ratios between the front wheels and the rear wheels for the respective wheel torque regions, and
 the comparison means compares the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with an average value of the rotating wheel speed ratio in a wheel torque region including the wheel torque obtained by the wheel torque calculation means. 
 
     
     
       4. The apparatus according to  claim 1 , wherein the initialization means includes a means for setting a plurality of wheel torque regions and for calculating, at a normal internal pressure, an average wheel torque value of the respective wheel torque regions and an average value of the rotating wheel speed ratios between the front wheels and the rear wheels, and a means for obtaining a reference straight line connecting the average values of the respective regions, and
 the comparison means compares the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained by the wheel torque calculation means and the reference straight line. 
 
     
     
       5. An apparatus for detecting a tire attached to a vehicle having a decreased air pressure, comprising:
 a rotation velocity detection means for periodically detecting rotation velocities of tires of the respective wheels of the vehicle; 
 a rotating wheel speed ratio calculation means for calculating, based on rotation velocity information obtained from the rotation velocity detection means, a rotating wheel speed ratio between front wheels and rear wheels of the vehicle for a predetermined plurality of speed regions; 
 a wheel torque calculation means for calculating a wheel torque of the vehicle; 
 an initialization means for obtaining a relation at a normal internal pressure between the wheel torque and the rotating wheel speed ratio between the front wheels and the rear wheels for the respective speed regions; 
 a storage means for storing the relation obtained by the initialization means; 
 a comparison means for comparing, for the respective speed regions, the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained by the wheel torque calculation means and the relation stored by in storage means; and 
 a judgment means for judging whether a tire air pressure is decreased or not based on a comparison result by the comparison means. 
 
     
     
       6. The apparatus according to  claim 5 , wherein the initialization means includes a means for obtaining, for the respective speed regions, a relation at a normal internal pressure between the wheel torque and the rotating wheel speed ratio between the front wheels and the rear wheels based on a regression line, and
 the comparison means compares, for the respective speed regions, the rotating wheel speed ratios obtained by the rotating wheel speed ratio calculation means with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained by the wheel torque calculation means and the regression line. 
 
     
     
       7. The apparatus according to  claim 5 , wherein the initialization means includes a means for setting a plurality of wheel torque regions for the respective speed regions and for calculating, at a normal internal pressure, an average value of the rotating wheel speed ratios between the front wheels and the rear wheels for the respective wheel torque regions, and
 the comparison means compares, for the respective speed regions, the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with an average value of the rotating wheel speed ratios in a wheel torque region including the wheel torque obtained by the wheel torque calculation means. 
 
     
     
       8. The apparatus according to  claim 5 , wherein the initialization means includes a means for setting, for the respective speed regions, a plurality of wheel torque regions, and for calculating, at a normal internal pressure, an average value of wheel torques for the respective wheel torque regions and an average value of the rotating wheel speed ratios between the front wheels and the rear wheels, and a means for obtaining a reference straight line connecting the average values of the respective regions, and
 the comparison means compares, for the respective speed regions, the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained by the wheel torque calculation means and the reference straight line. 
 
     
     
       9. A method for detecting a tire attached to a vehicle having a decreased air pressure, comprising:
 a rotation velocity detection step of periodically detecting rotation velocities of tires of the respective wheels of the vehicle; 
 a rotating wheel speed ratio calculation step of calculating, based on rotation velocity information obtained in the rotation velocity detection step, a rotating wheel speed ratio between front wheels and rear wheels of the vehicle; 
 a wheel torque calculation step of calculating a wheel torque of the vehicle; 
 an initialization step of obtaining a relation at a normal internal pressure between the wheel torque and the rotating wheel speed ratio between the front wheels and the rear wheels; 
 a storage step of storing the relation calculated in the initialization step; 
 a comparison step of comparing the rotating wheel speed ratio with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque and the stored relation; and 
 a judgment step of judging whether a tire air pressure is decreased or not based on a comparison result obtained in the comparison step. 
 
     
     
       10. The method according to  claim 9 , wherein the initialization step includes a step of obtaining a relation at a normal internal pressure between the wheel torque and the rotating wheel speed ratio between the front wheels and the rear wheels based on a regression line, and
 the comparison step compares the rotating wheel speed ratio obtained in the rotating wheel speed ratio calculation step with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained in the wheel torque calculation step and the regression line. 
 
     
     
       11. The method according to  claim 9 , wherein the initialization step includes an average value calculation step of setting a plurality of wheel torque regions and of calculating, at a normal internal pressure, an average value of the rotating wheel speed ratios between the front wheels and the rear wheels for the respective wheel torque regions, and
 the comparison step compares the rotating wheel speed ratio obtained in the rotating wheel speed ratio calculation step with an average value of the rotating wheel speed ratio in a wheel torque region including the wheel torque obtained in the wheel torque calculation step. 
 
     
     
       12. The method according to  claim 9 , wherein the initialization step includes an average value calculation step of setting a plurality of wheel torque regions and of calculating, at a normal internal pressure, an average wheel torque value of the respective wheel torque regions and an average value of the rotating wheel speed ratios between the front wheels and the rear wheels, and a step of obtaining a reference straight line connecting the average values of the respective regions, and
 the comparison step compares the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation step with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained by the wheel torque calculation step and the reference straight line. 
 
     
     
       13. A method for detecting a tire attached to a vehicle having a decreased air pressure, comprising:
 a rotation velocity detection step of periodically detecting rotation velocities of tires of the respective wheels of the vehicle; 
 a rotating wheel speed ratio calculation step of calculating, based on rotation velocity information obtained in the rotation velocity detection step, a rotating wheel speed ratio between front wheels and rear wheels of the vehicle for a predetermined plurality of speed regions; 
 a wheel torque calculation step of calculating a wheel torque of the vehicle; 
 an initialization step of obtaining a relation at a normal internal pressure between the wheel torque and the rotating wheel speed ratio between the front wheels and the rear wheels for the respective speed regions; 
 a storage step of storing the relation obtained in the initialization step; 
 a comparison step of comparing, for the respective speed regions, the rotating wheel speed ratio with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque and the stored relation; and 
 a judgment step of judging whether a tire air pressure is decreased or not based on a comparison result in the comparison step. 
 
     
     
       14. The method according to  claim 13 , wherein the initialization step includes a step of calculating a relation for the respective speed regions at a normal internal pressure between the wheel torque and the rotating wheel speed ratio between the front wheels and the rear wheels based on a regression line, and
 the comparison step compares, for the respective speed regions, the rotating wheel speed ratio obtained in the rotating wheel speed ratio calculation step with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained in the wheel torque calculation step and the regression line. 
 
     
     
       15. The method according to  claim 13 , wherein the initialization step includes an average value calculation step of setting a plurality of wheel torque regions for the respective speed regions and of calculating, at a normal internal pressure, an average value for the respective wheel torque regions of the rotating wheel speed ratios between the front wheels and the rear wheels, and
 the comparison step compares, for the respective speed regions, the rotating wheel speed ratio obtained in the rotating wheel speed ratio calculation step with an average value of the rotating wheel speed ratio in a wheel torque region including the wheel torque obtained in the wheel torque calculation step. 
 
     
     
       16. The method according to  claim 13 , wherein the initialization step includes an average value calculation step of setting a plurality of wheel torque regions for the respective speed regions and of calculating, at a normal internal pressure, an average wheel torque value of the respective wheel torque regions and an average value of the rotating wheel speed ratios between the front wheels and the rear wheels and, a step of obtaining a reference straight line connecting the average values of the respective regions, and
 the comparison step compares, for the respective speed regions, the rotating wheel speed ratio obtained in the rotating wheel speed ratio calculation step with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained in the wheel torque calculation step and the reference straight line. 
 
     
     
       17. A program for causing, in order to detect a decrease in an air pressure of a tire attached to a vehicle, a computer to function as; a rotating wheel speed ratio calculation means for calculating, based on rotation velocity information obtained from a rotation velocity detection means for periodically detecting rotation velocities of tires of the respective wheels of the vehicle, a rotating wheel speed ratio between front wheels and rear wheels of the vehicle; a wheel torque calculation means for calculating a wheel torque of the vehicle; an initialization means for obtaining a relation at a normal internal pressure between the wheel torque and the rotating wheel speed ratio between the front wheels and the rear wheels; a comparison means for comparing the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained by the wheel torque calculation means and the relation obtained by the initialization means; and a judgment means for judging whether a tire air pressure is decreased or not based on a comparison result by the comparison means. 
     
     
       18. The program according to  claim 17 , wherein the initialization means includes a means for obtaining a relation at a normal internal pressure between the wheel torque and the rotating wheel speed ratio between the front wheels and the rear wheels based on a regression line, and
 the comparison means compares the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained by the wheel torque calculation means and the regression line. 
 
     
     
       19. The program according to  claim 17 , wherein the initialization means includes a means for setting a plurality of wheel torque regions and for calculating, at a normal internal pressure, an average value of the rotating wheel speed ratios between the front wheels and the rear wheels for the respective wheel torque regions, and
 the comparison means compares the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with an average value of the rotating wheel speed ratio in a wheel torque region including the wheel torque obtained by the wheel torque calculation means. 
 
     
     
       20. The program according to  claim 17 , wherein the initialization means includes a means for setting a plurality of wheel torque regions and for calculating, at a normal internal pressure, an average wheel torque value of the respective wheel torque regions and an average value of the rotating wheel speed ratios between the front wheels and the rear wheels, and a means for obtaining a reference straight line connecting the average values of the respective regions, and
 the comparison means compares the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained by the wheel torque calculation means and the reference straight line. 
 
     
     
       21. A program for causing, in order to detect a decrease in an air pressure of a tire attached to a vehicle, a computer to function as; a rotating wheel speed ratio calculation means for calculating, based on rotation velocity information obtained from a rotation velocity detection means for periodically detecting rotation velocities of tires of the respective wheels of the vehicle, a rotating wheel speed ratio between front wheels and rear wheels of the vehicle for a predetermined plurality of speed regions; a wheel torque calculation means for calculating a wheel torque of the vehicle; an initialization means for obtaining a relation at a normal internal pressure between the wheel torque and the rotating wheel speed ratio between the front wheels and the rear wheels for the respective speed regions; a comparison means for comparing, for the respective speed regions, the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained by the wheel torque calculation means and the relation obtained by the initialization means; and a judgment means for judging whether a tire air pressure is decreased or not based on a comparison result by the comparison means. 
     
     
       22. The program according to  claim 21 , wherein the initialization means includes a means for obtaining, for the respective speed regions, a relation at a normal internal pressure between the wheel torque and the rotating wheel speed ratio between the front wheels and the rear wheels based on a regression line, and
 the comparison means compares, for the respective speed regions, the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained by the wheel torque calculation means and the regression line. 
 
     
     
       23. The program according to  claim 21 , wherein the initialization means includes a means for setting a plurality of wheel torque regions for the respective speed regions and for calculating, at a normal internal pressure, an average value of the rotating wheel speed ratios between the front wheels and the rear wheels for the respective wheel torque regions and,
 the comparison means compares, for the respective speed regions, the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with an average value of the rotating wheel speed ratio in a wheel torque region including the wheel torque obtained by the wheel torque calculation means. 
 
     
     
       24. The program according to  claim 21 , wherein the initialization means includes a means for setting, for the respective speed regions, a plurality of wheel torque regions and for calculating, at a normal internal pressure, an average value of wheel torques for the respective wheel torque regions and an average value of the rotating wheel speed ratios between the front wheels and the rear wheels, and a means for obtaining a reference straight line connecting the average values of the respective regions, and,
 the comparison means compares, for the respective speed regions, the rotating wheel speed ratio obtained by the rotating wheel speed ratio calculation means with the rotating wheel speed ratio at a normal internal pressure obtained from the wheel torque obtained by the wheel torque calculation means and the reference straight line.